Aerial system



AERIAL SYSTEM Filed Nov. 7, 1946 www,

Patented May 23, 1950 UNITED STATES AERIAL SYSTEM Dudley HalesToller-Bond, London, England, as-

signor to The Decca Record Company, Limited,

London, Britain England, a corporation of Great Application November 7,1946, Serial No. 708,284 In Great Britain November 6, 1945 Section 1,Public Law 690, August 8, 1946 Patent expires November 6, 1965 Thisinvention relates to aerial systems and has particular reference toaerial or antenna constructions which nd particular utility whenemployed as radiators or radio frequency energy of relatively longwavelength.

In the radio transmitting art, great diiculty has been experienced inthe past in obtaining a reasonably nigh radiation ei'iiciency. This isfor the reason that with antenna constructions employed prior to thisinvention, it was diiiicult, if not impossible, to obtain a relativelyhigh radiation resistance. As is well known, the radiation eiiiciency isequal to the ratio of the radiation resistance to the sum of theradiation resistance, ground resistance and circuit resistance. 'Sincethe radiation resistance is proportional to the square of the effectiveheight of the antennae in wavelengths, and since at low frequencies itis impossible to erect a mast or tower which is comparable to a quarterwavelength in height, it becomes impossible with conventionalconstructions to erect an antenna in which the radiation resistancebears a favourable ratio to the ground resistance. Accordingly, at best,the radiation efficiency of conventional installations is much lowerthan is desired.

Furthermore, since at low frequencies the height of conventionalinstallations is low as compared with the wavelength of the signalstransmitted, the inductance and capacity of the radiator are too low forresonance and a series loading coil must be included in the circuit.This adds additional resistance to the non-radiating parts of thecircuit and further reduces the radiation eiiiciency.

Many prior attempts have been made to improve the radiation eiciency atlow frequencies and these attempts have generally taken the form of flattop antennae where a considerable length of radiator is disposedparallel to the surface of the ground. The cost of such constructions isconsiderably increased, due to the necessity for erecting two supportingtowers instead of one. Furthermore, the two towers, not forming part ofthe radiating structure, absorb energy radiated from the antenna andtend to offset the gains in efficiency to be expected from the flat topconstruction. Also, where the radiations are to be used for navigationalor'direction finding purposes, further disadvantages of the fiat topconstruction are found in the non-circular radiation pattern produced,and in the horizontal polarization of the radiation which tends toincrease the sky wave difficulties, particularly at night.

It is. therefore, an object of this invention to provide an antenna orradiator for use at relatively low frequencies which overcomes the abovenoted disadvantages by providing a higher radia- 2 Claims. (Cl. Z50-33)tion resistance and lower ground resistance than is found in smiplevertical radiators of the same height.

It is also an object of this invention to provide an antenna of thecharacter described in the preceding paragraph in which an array ofradiators is so arranged that the cross-section area of the arrayincreases away from the transmitter.

It is another object of this invention to provide an antenna of thecharacter referred to in the preceding paragraphs which comprises agroup of radiating conductors so disposed as to define a conical shapepositioned with the apex thereof nearest the ground.

' It is a still further object of this invention to provide an aerialsystem of the character hereinbefore referred to which has a largeradiating surface to thereby provide an antenna having high capacity.

l It is also an object of this invention to provide an antennaconstruction of the character hereinbefore referred to which includes asingle supporting mast.

It is a still further object of this invention to provide an antennaconstruction of the character set forth in the preceding paragraphswhich is symmetrical in horizontal cross-section to provide a circularradiation pattern.

^ It is another object of this invention to provide an antenna of thecharacter hereinbefore described in which the current is fed to theradiators in such manner as to provide an effective height greatlyexceeding one half of the actual height.

Other objects and advantages of this invention will be apparent from astudy of the following specications, read in conjunction with theaccompanying drawings, wherein the single gure is a perspective view ofthe preferred embodiment of this invention.

Referring to the drawings, there is illustrated an antenna constructedin accordance with the principles of this invention and characterizedparticularly by the employment of a single mast or tower as theprincipal element of the supporting structure. This tower, which isshown at 30, may be of any suitable or conventional construction and ispreferably disposed vertically and insulated from ground as by means ofsuitable tower insulators (not shown) placed between the lower ends ofthe tower legs and the base structure upon which the tower is erected.

From the top of the tower there are extended a plurality of guys 3 I,which are anchored at their outer ends as by means of ground stakes oranchors 32. Each 'of the guys 3| is interrupted at approximately the midpoint by means of strain insulators 33 so that the upper half only ofeach of the guy members is associated with( the,

3 radiating ...structure Auxiliary Lconductors .or feeder lines 34 maybe connected to the upper half of each of the guy members 3l at or nearthe location of the strain insulators 33, each of the conductors 34being extended to and con? nected to the lower end of the tower t. Addietional capacity may be provided by means of 'a plurality ofcircumferentially extending conductors 35, 36, 37, etc., which aresecured to the upper halves of the guys 3| and Vwhich are "arranged ingenerally circular form as viewed in plan.

The antenna may be fed by a singlelead 38 non nected to the base of themast 39 and extended' from a suitable transmitter house or shelter 39vdisposed a convenient distance away from the tower.

` It will be noted that 'the invention described herein embodies 'theprinciple of providing 'an array of radiating conductors which are sodisposed as to deiine a conical or semi-'conical shape in which the apexof the cone' is located nearest the ground. As will 'be understood, asingle Avertical W'ire antenna which 'is short compared to thewavelengths of the signal to be radiated'therefrom 'has neither sufcientcapacity nor inductance to resonate at 'the frequency desired 'to beresonated. 'Such'an antenna maybe tuned by the addition of a seriesloading coil, but this reduces 'the radiation eiiiciency. Each oi theantennae described herein substitutes additional capacity for theseriesloading lnductors, the additional capacity being achieved throughlthe use of a large number of radiating conductors so as to provide alarger surface area. Preferably to .increase the surface area and toreduce the resistance due to 'skin ei'iect, each of the radiatingconductors is 'formed of multi-strand `cable or similar 'high eiliciencyradio frequency conductor.. Additional capacity is included by employingtheA supporting structure as part oi the radiating array. Furthermore,by concentra-ting .a great part of the 'surface area of the radiatingarray in thatarea which islocated high above the ground, the effectiveheight of the antenna is increased so as to increase the radiationresistance.

lt 'has'been rfound that with antennae `con'- struc'ted asde'scribedheren wherein alarge nurnber of paths are provided for theflow of radio frequency current to the yhigh capacity elements of thestructure, the current concentration in each of 'the conductors is suchas to place the eilective'height ofthe antenna `well above the .midpoint-of the actual height. Furthermore the distribution of the lines of-force about .the .structure as 'a 'whole appears to be such as toreduce the ground resistance to a value materially lower `than thatassociated with a simple vertical conductor of 'the same height. Theground resistance is further reduced 'by using a network of groundconductors which are buried a .convenient distance below' the surface ofthe ground and extended 'radially away from the base ci the antenna adistance which is comparable to the height of 'the structure.

Thus, Vthrough an Vincrease in the ratio of radiation resistance to.ground resistance, an improvement in radiation eiliciency vby a. factoro'f six or more is readily obtainable.

It should also be noted that the elimination (or the reduction 'in size)ofthe series 'loading coil required 'for a single vertical radiatormaterially reduces the circuit losses and also ,provides a lower ratioof antenna reactance to transmission resistance, thereby providing arelatively broad tuning antenna. A broadly tuned antenna willefficiently radiate a wider band of frequencies and will also producesmaller phase changes as the result of varying external conditions, anitem of considerable importance when the antenna is used in radioVriefigation and beacon systems operating on the phase 'comparisonprinciple.

'From 'the 'foregoing it will be observed that this invention provides anew aerial system which is lchara'cterized by high capacity, highradiation resistance, low ground resistance, and .louT .ratio of.antenna reactance to radiation reeistance. It lwill also be noted thatthe construction employed is such as to reduce to a minimum the amountof structure which must be erected, thus Yproviding a denite advantageover the conventional flat top constructions which require a 'minimum oftwo supporting towers. It 'should also be noted that 'the structuredisclosed herein is symmetrical about a vertical centre line and'therefore operates to radiate a 'truly circular 'field strengthpattern.

While 'there has been shown and described the preferred embodiment of'the invention, 'the invention is not to be limited to any of 'the de#tails shown or described 'herein except as 'cleiin'ed Ain the appendedclaims.

1. 'In 'an 'antenna system, 'the combination of: a'supporting towerextending upwardly from the ground surface; a plurality oi radiatingconducto'rs extending upwardly and outwardly vfrom the Tower end 'o'fsaid tower, said conductors being disposed outside of .said tower for'their entirelength; means connected to said tower for holding 'the'upper 'portions o'f said conductors' spaced "from each other and spaced'from said tower; means connecting 'the upper ends of said conductors tothetop of said tower; means insulating said tower l'from ground; andmeans electrically 'interconnecting said conductors .with said tower.

2. In an antenna system, the combination of: a supporting "towerextending upwardly .'from the "ground smface'; `means insulating `said.tower l fromgroun; a plurality 'o'f circum'feren'tially4 spaced ,guys'extending 'from 'the .top o'f 2said tower tothe `ground 'at jp'in'tsspaced [from .said tower; an insulator 'in each of vsaid y,guyselectrically dividing the same into an -upper ,pori tion and a vlowerportion; Aand -a zplurality Yfof radiating conductors, -each extendingupwardly and outwardly from the lowerend .of said tower and `eachxelectricallyf-connected ato Athe .upper .portion of adiieren't.one ofsaid iguys.

DUDIJEYSHALES FOLDER-BOND.

.REFERENCES iCIlED 'The liollow'ing references "are of record in 'theil'e foi this patent:

STATES .PATENTS Number Name "Date *423;067 Melber "l\7lfar. "lil, T8901563997257 Eraser iling. 23, iloa-'I -2,01l4;!'84 Schiller 5Sept.117,51935 .223014385 .Schuler `ISept. 21??, 'T935 2;952i846 'Ve'nable*Dec 1, :T936 232625,46'0 G`erth- Nov. S, HMI 2,267,613 Lindenblad A'De'c. 23,"219-41 r2,2 8;560 Peters fApl. 1,-19'42 FGREIGN PATENTSNumber 'Country Date l "248;597 'Great'Brltain Mar. 11,1925

